Liquid mixing and dispensing apparatus

ABSTRACT

An apparatus for mixing and spraying or dispensing two liquids, such as liquid organic resins and polyisocyanates which react to form a polyurethane foam. The apparatus comprises a gun and related equipment and includes a reciprocally mounted valving rod in the gun which during its movement is bathed in a third liquid which assures the easy movement of the rod. In the case of the organic resin and polyisocyanates, the third liquid which is known as &#39;&#39;&#39;&#39;cellosolve&#39;&#39;&#39;&#39; solvent prevents the reaction of the reagents thereby preventing the formation of polyurethane foam within the dispensing apparatus which formation would inhibit the movement of the valving rod. The valving rod is such that the free end thereof controls the on/off flow of the two liquids into a mixing chamber.

United States Patent Sperry Aug. 29, 1972 54 LIQUID MIXING ANDDISPENSING APPARATUS [72] Inventor: Charles R. Sperry, Providence, RI.

[73] Assignee: Instapak Corporation, Darien,

Conn.

[22] Filed: Jan. 18, 1971 [21] App1.No.: 107,023

[52] US. Cl. ..239/112, 239/117, 239/414 [51] Int. Cl. ..B05b 15/02 [58]Field of Search ..239/106, 112, 117, 118, 409,

[56] References Cited UNITED STATES PATENTS 3,144,210 8/1964 Levy..239/116 X 1,332,544 3/1920 Davis ..239/41l 3,263,928 8/ 1966 Gusmer..239/414 X 3,291,396 12/1966 Walter ..239/355 X 3,504,855 4/1970 Volkcr..239/112 3,417,923 12/1968 Carlson ..239/1 12 PrimaryExaminer-M.-Henson Wood, Jr. Assistant Examiner-John J. LoveAtt0rney-Siegel and Geren [57] ABSTRACT An apparatus for mixing andspraying or dispensing two liquids, such as liquid organic resins andpolyisocyanates which react to form a polyurethane foam. The apparatuscomprises a gun and related equipment and includes a reciprocallymounted valving rod in the gun which during, its movement is bathed in athird liquid which assures the easy movement of the rod. In the case ofthe organic resin and polyisocyanates, the third liquid which is knownas cellosolve solvent prevents the reaction of the reagents therebypreventing the formation of polyurethane foam within the dispensingapparatus which formation would inhibit the movement of the valving rod.The valving rod is such that the free end thereof controls the on/offflow of the two liquids into a mixing chamber.

10 Claims, 3 Drawing Figures Patented Aug. 29, 1972 3,687,370

77 INVENTOR.

CHARLES R SPERRY I BY f 82 86 86 REL/5.

1 LIQUID MIXING AND DISPENSING APPARATUS BACKGROUND OF THE INVENTION 1This invention relates to an apparatus for mixing and dispensing aplurality of liquids; and in particular is related to an apparatus formixing and dispensing of the reactants for forming polyurethane foam.

An apparatus for producing a uniform homogenous mixture of a pluralityof liquids has been in great demand. In particular, the preparation ofpolyurethane foams requires the uniform mixing of liquid organic resinswith polyisocyanates; moreover, it is particularly desirable to dispensethis isocyanate-resin mixture into a receptacle, for example, a package,before it has reacted to form the polyurethane foam. This is desirable,for example, when attempting to build up the foam structure around someobject as in packaging. One particular problem with the handling of thepolyurethane foam material is that the organic resin and isocyanate tendto react relatively rapidly and can foam within the various passagewayin the dispensing apparatus and then the foam is most difficult toremove.

Considerable effort has been spent in attempting to thereby inhibitingthe flow of the materials within or out of the apparatus. In theextreme, the passageways do become blocked within a relatively shorttime.

U.S. Pat. No. 3,263,928, Apparatus for Ejecting a Mixture of Liquidsissued Aug. 2, 1966, discloses a gun-type apparatus for mixing anddispensing a plurality of liquids which is particularly suitable for usewith polyurethane foams. The apparatus disclosed in the patentrepresents an improvement over the patentees previous invention asdisclosed in U.S. Pat. No. 2,890,836 wherein substantially complete airpurging of the mixing chamber was provided upon the discontinuance ofthe operation of the gun. In U.S. Pat. No. 3,263,928 the patentee hasprovided a mixing chamber which is cylindrical in shape and throughwhich there is a valving rod of about the same diameter as the chamber.When the valving rod is in the retracted posi tion, the pressurizedliquids enterthe'mixing chamber from their respective sources and themixed liquids.

then exit from the front of the gun. When the valving rod is movedforwardly, it closes off the entrance ports and scores or mechanicallyabrades the surface of the mixing chamber so as to remove any of themixture therefrom and prevent the hardening and jamming of the valvingrod. The valving rod is moved forwardly until a small end portionprotrudes from the front end of the gun. An arrangement is provided atthe front endof the gun whereby compressed air is directed along thefront of the valve housing for the purpose of cleaning the front end ofthe spray apparatus. This was provided, principally, to clean theprotruding end portion of the valve rod. Thus, any accumulation ofdeposits of spray materials about the outlet of the spray equipment wasto be avoided. It will be understood that had the pate'n-' tee not takenthat approach, the spray materials could harden on the protruding endportion of the valve rod thereby making it extremely difficult toretract the valving rod for the next spraying operation. In addition,there is some foam hardening in the mixing chamber, even in the form ofa thin film. All of these provisions, not withstanding very highpressures, are still necessary to unseat the valving rod from its closedposition. Furthermore, these arrangements required another compressedair line to be attached toward the front end of the gun in addition tothe air lines necessary in order to move the valving rod back and forth.

The gun as taught in said patent has had the practical drawbacks asmentioned above which include the requirement of the additional air linefor the cleaning of the gun and the high forces required to unseat theclosed valving rod. In operation a frequent cleaning cycle has beenrequired.

SUMMARY OF THE INVENTION By virtue of this invention there is providedan apparatus for mixing and dispensing a plurality of liquids and inparticular for mixing and spraying or otherwise dispensing polyurethanefoam. The apparatus is formed in the general shape of a gun within thebarrel of which is provided a reservoir which is filled with a materialsuch cellosolve solvent that prevents the reaction of the polyurethanefoam precurser materials. In addition, a lubricant may also be providedin said reservoir. The flow of the liquid reactants is controlled by avalving rod, the forward portion of which is bathed in a material suchas cellosolve when the rod is in the retracted or open position; in theclosed position the coated rod passes into the mixing chamber and thefront end of the rod may be flush with the front end of the gun. Coatingof the rod and passageway prevents the formation of the foam within thepassageway thereby eliminating the problem of clogging or jamming of thevalve rod, or closing of the passageways by the formation of the foam insitu. Since foaming within the mixing chamber is prevented, the forcesrequired to move the valving rod to permit the mixing and dispensing ofthe reactants are significantly reduced. Moreover, by preventing thereaction, only one air line is required to move the valve rod and thesecond air line of the prior art has been eliminated. The elimination ofthis air line thus provides a more easily handled apparatus. Moreimpori-tantly my apparatus is readily used in intermittent polyurethanefoam dispersing without the need for clean-up at short intervals.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing theouter configuration of the gun of this invention;

FIG. 2 is a cross-sectional view showing the inner mechanism of thepresent apparatus in the closed condition; and

FIG. 3 is a cross-sectional view similar to FIG. 2 with the exceptionthat the apparatus is in the dispensing condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the figures, agun 10 generally is shown which comprises two basic assemblies: thebarrel assembly 12 and the handle assembly 14. The handle assembly isprovided with an actuating button or trigger 16 and compressed air inlet18. A pair of ports for the entry of the organic resin and isocyanateare provided in the forward section 19 of the barrel assembly 12. InFIG. 1, the ports 20 and 22 are shown aligned in a vertical plane.However, it will be understood that the ports may also be aligned in thehorizontal plane as well as their associated passageways as shown inFIGS. 2 and 3. From FIG. 2 it can be seen that the rearward portion 23of the barrel 12 is essentially a hollow thin-walled cylinder. Theforward section 19 could be considered as a solid frusto-conical sectionhaving a bore 24 coaxial with the longitudinal axis thereof which bore24 opens into the rearward cylindrical section 23. A second set ofpassageways 26 and 28 are provided which extend from the ports 20 and 22and intersect the central bore 24.

A generally T-shaped flanged reservoir forming member 30 is disposedwithin the barrel 12. The member 30 has a flange or head section 32, theouter diameter of which is approximately equal to the inner diameter ofthe rearward cylindrical section 23. An annular groove 33 is providedabout the periphery of the head section 32 and an O-ring 34 is disposed,therein. Thus when the member 30 is in position, a seal is created onthe inner periphery of the cylindrical section 23. Extending forwardlyfrom the head section 32 is a shank portion which comprises two sectionsof reducing diameter. The first intermediate section 36 has a diametergreater than the diameter of bore 24 so that when the member 30 is inplace the shoulder 38 will abut or bottom out on'the front inner surfaceof the cylindrical section 23. Extending forwardly from the intermediatesection 36 is a forward reduced section 40. The outer diameter of thissection is slightly larger than the diameter of the bore 24 thus whensection 40 is inserted into the base a pressfit seal is created. Thelength of the section 40 is such that when the shoulder 38 abuts thefront surface of the inner cylinder, the forward end 42 if the section40 is positioned in the forward end of the frustro-conical section 19.

The reservoir forming member 30 is provided with an axial bore 44through which a valving rod 46 is adapted to move. In the forwardreduced section 40 there is further provided a pair of passageways 48and 50 which provide communication between the passageways 26 and 28 andthe portion of the bore 44 in the forward shank section 40. When thevalving rod is in the retracted position (as is illustrated in FIG. 3),fluids will flow from port 20 through passageway 26 through thepassageway 48 and into the bore 44; similarly, a second fluid will flowfrom the inlet port 22 through the passageway 28 through the passageway50 and into the bore 44.

Returning to FIG. 2 and continuing with the description of the T-shapedmember 30, it will be seen that the bore 44 also extends through thehead section 32 and a slot 52 is provided which extends diametricallyclear through the intermediate shank portion 36. Some portion of thevalving rod 46 is at all times disposed within the slot 52 and theforward portion of the rod 46 is always within the bore 44 in theforward section 40.

When the member 30 isin place, an annular chamber is created which isdefined by the inner diameter and forward inner surface of thecylindrical section 23, by the outer diameter of the intermediate shanksection 36 and the front facing surface of the head 32. This annular orring-like space is continuous and communicates with the space withinslot 52. In operation the annular space and slot are filled with thereaction preventative fluid, cellosolve so the portion of the rod 46which is within the slot 52 is always exposed and bathed in cellosolve.Thus, as the valving rod 46 travels forwardly and rearwardly during itsmovement, substantially the entire rod is bathed in cellosolve.

The rearward end of the valving rod 46 is mounted to a pneumaticallymoveable piston 54, the movement of which controls the movement of therod 46. The periphery of forward end 56 of the piston sealingly andslideably engages the inner surface of the cylindrical section 23. Tofurther assure sealing engagement, an O- ring 58 is disposed in anannular groove within the.

periphery of the forward end 56. The center section 60 of the piston 54is of reduced diameter and the rearward end 62 has a diameterapproximately that of the inner diameter of the section 23. A pluralityof passageways 64 are provided in the rearward section 62 forcommunication between the space 63 behind the rearward section 62 and anannular space formed by the piston, its reduced center section 60 andthe inner surfaceof the cylindrical section 23. In its forward movement,the front end of the piston 54 abuts the rearward end of the T-shapedreservoir forming member 30. In that configuration, as shown in FIG. 2,the forward end of the valving rod 46 is positioned in the forward endof the front reduced section 40.

Turning now to FIG. 3, it will be seen that the piston 54 is in therearward retracted position. A back sealing and stop plate 66 is mountedto the rearward end of the barrel 12 and an annulus is provided in theouter diameter of the plate 66 with an Oring 68 being disposed therein.When the back plate 66 is in place, the rear bore of the cylindricalsection 23 is completely sealed. A locking ring 70 which engages anunder cut groove is provided rearwardly of the sealing plate 66 so as tohold the sealing plate in position. As is seen in FIG. 3, the forwardend of the valving rod 46 is retracted to a position rearward of thepassageways 48 and 50 but slightly forward of the front end of the slot52. If the valving rod 46 were permitted to retract into the slot 52, itmay be difficult to reinsert the front end of the rod 46 in the bore 44.However, within that limitation it will be appreciated that it isdesirable to expose the largest possible surface of the valving rod 46to the cellosolve within the reservoir. However, this must be balancedagainst the problems of guiding the rod 46 into the bore 44.

As indicated above, the piston is moved forwardly and rearwardlypneumatically; however, it will be appreciated that hydraulic means orother similar means for moving the valving rod and/or piston forwardlyto the closed position or rearwardly to the open and retracted positioncan be used.

Returning now to FIG. 2, the pneumatic mechanism for moving the valvingrod 46 will be described. As is seen, two ports 72 and 74 are providedin the bottom of the cylindrical section 23. These ports and the piston54 are arranged such that the port 72 is always in a position forward ofthe front end 56 of the piston 54.

The rearward port 74 is positioned so that it will always be rearward ofthe back surface 76 of the forward section 56. The principle ofoperation is readily understood in that in order to move the piston andhence valving rod rearwardly, compressed air is flowed into the port 72which causes the piston 54 to move rearwardly. As the piston movesrearwardly, gas or air caught between the sealing plate 66 and the backend 62 of the piston 54 can flow through the venting ports 64 and henceout through the port 74. Referring back to FIG. 3, in order to move thepiston 54 and valving rod 44 forwardly, the air flow is reversed and airis introduced through the port 74 thus exerting force on the backsurface 76 of the front end 56 of the piston thereby moving the pistonforwardly. This piston is permitted to move forwardly until the frontend 56 abuts the rear end of the T-shaped member 30.

The handle 14 provides the mechanism for controlling the movement of thecompressed air so as to accomplish the desired movement of the pistonand hence the valving rod. This mechanism includes the three principalparts of the handle 14, the air inlet coupling 18 and the actuatingbutton 16.

Again referring to FIG. 2 and the handle assembly 14, there is provideda pair of passageways 77 and 78 which are aligned with the ports 72 and74. The lower end of both of these passageways 77 and 78 communicateswith a central passageway 80 in which the actuating button 16 moves. Theair inlet coupling 18 provides communication between a source ofcompressed air and the passageway 80. An atmosphere venting passageway82 is provided in the lower portion of the handle and is positioned tointersect the passageway 80 so that in all of the various arrangements,air which is exhausted from the cylindrical section 23 by the piston 54vents to atmosphere therethrough. This is necessary in order to preventa build-up or back pressure which would inhibit the movement of thepiston. The actuating button 16 is a double purpose member, the firstpurpose of which is to actuate the mechanism for moving the valving rodand the second purpose of which is to provide passageways for themechanism. As can be seen, the button 16 is provided with three annulargrooves. One annular groove 84 is located atthe rearward end of thebutton 16, while the remaining grooves 86 and 88 are locatedapproximately midway between the forward and rearward ends of the button16. An axial passageway 90 extends from the rearward end of the button16 to a point intermediate the two midway positioned annular grooves 86and 881A cross hole or passageway 92 is drilled diametrically throughthe button l6 and intersects the passageway 90.

A retaining washer 94 is mounted to the button 16 so as to create aninterference or jamming fit between the passageway 80 and the button 16thereby preventing it from being expelled or pushed from the passageway80 air 97 is coupled at 18 to the central passageway 80. In the closedposition as seen in FIG. 2 the valving rod 44 extends past the ports 48and 50 thereby preventing the flow of the resin and isocyanate. In thatconfiguration, air flowing from the coupling 18 flows into the centralpassageway and pushes the button 16 forwardly such that the O-ring inthe groove 84 sealingly engages the surface rearward of the atmosphereventing passageway 82 and forward of the inlet passageway 78. Thus thegas flows from the passageway 80 into the passageway 78 through the port74 against the back surface 98 of the piston 54 through the ports 64 andagainst the back surface 76 of the forward end of the piston 54. In thisconfiguration, the front end of the piston bottoms out or abuts the rearend of the T- shaped member 30. Gas which was caught between the frontend of the piston 54 and the rear end of the chamber forming member 30is expelled through the port 72 and passageway 77. When the exhaustedgas reaches the passageway 80, it flows through an annular space whichis created about the button 16 by the O- ring in the rearward groove 84and an O-ring in the central groove 86. The O-ring in the groove 86contacts the surface forward of the passage 77. Thus, as is seen by thearrows, the exhausted gas will go around the button 16 and vent to theatmosphere through the passageway 82. In this position, the centralportion of the valve rod 46 is bathed in the cellosolve disposed withinits reservoir. In order to actuate the gun for mixing and spraying, thebutton 16 is retracted as shown in FIG. 3. When the button is retracted,the O-ring in the rearward groove 84 is caused to engage the surfacerearward of the passageway 78 thereby sealing the passageway 78 from theinward flow of air. Air then flows from the coupling 18 into thepassageway 80 and from there into the central passageway within thebutton 16. When the button 16 is in the rearward position, the O-ring inthe groove 86 then contacts the surface rearward of lower end passageway77 and forward of the passageway 82. The O-ring in the groove 88 stillcontacts the surfaces forward of the lower end of passageway 77. The airthen flows down the passageway 90, through and out from the cross hole92 and into the passageway 90, through and out from the cross hole 92and into the passageway 77. From the passageway 77, the compressed airflows through the port 72 and from there against the front surface ofthe piston 54. This causes the piston 54 to move rearwardly and thuscauses the gas between the piston 54 and the sealing plate 66 to flowoutwardly through the port 74 and passageway 78. The exhausted gas thenreaches the central passageway 80 and is prevented from flowingrearwardly by the O-ring in the groove 84 and from flowing forwardly bythe O-ring in the groove 86. However, the gas can flow in the annularchamber formed about the button 16 by the O-rings and the passageway 80and from there vent to atmosphere through the passageway 82.

Turning now to the inflow of the liquid organic resin and isocyanate, itcan be seen that as the forward end of the rod 46 is retracted and movedpast the ports 48 and 50 there will be an inflow of the pressurizedresin and isocyanate. Since the front end of the rod is not retractedinto the slot, the back end of the bore 44 remains closed. Therefore,when the isocyanate and resin flow into the bore44, they will mix and,due to the respective pressures, will be forced or sprayed outwardlyfrom the end of the bore 44. Depending upon the pressures, the ejectionfrom the forward end can be a dropletlike spray. Furthermore, since theapparatus is in the form of a gun, the spray can be directed wheredesired. In the retracted position as seen in FIG. 3, almost the entireforward portion of the valving rod 44 is immersed in cellosolve. When itis desired to stop the spray, either the operator or some mechanicalmeans, releases the button 16 and the air pressure thus causes thebutton to move forwardly into the rest position. As this occurs thepiston and the valving rod move forwardly and the valving rod closes offthe entry ports 48 and 50. The rod thus forces the remaining isocyanateand resin outwardly and the cellosolve prevents any reaction fromoccuring between any remaining isocyanate and urethane within the gun10. This also acts to prevent any reaction at the tip or front end ofthe gun. Thus when it is desired to spray again and the valving rod iseasily retracted since there is no build-up or hardening of urethanefoam, the strength of which must be overcome before the valving rod canbe retracted.

As indicated above, one of the two primary reactants in the polyurethanefoam making process is a liquid organic resin which is sometimesreferred to as a polyol. These materials can be selected from the groupconsisting of polyethers, polyesters, polythioethers, polyesteramides,alkylene glycols and polyisocyanate modifications thereof, whichmaterials are characterized by a molecular weight of greater then 500and which have at least two reactive hydroxyl groups per molecule.Examples of the foregoing are poly (oxyethylene) glycols and poly(oxypropylene) glycols, or copolymers of these materials whichcollectively may be referred to as poly (oxyalkylene) ethers.

The other principal reactants in the polyurethane foam making reactionare aromatic or aliphatic polyisocyanates. This may also includesubstituted aromatic polyisocyanates. Representative examples of thesematerials include 2,4-toluene diisocyanate; 2,6- toluene diisocyanate;ethylene diisocyanate; ethylidene diisocyanate;propylene-1,2-diisocyanate; butylene- 1,2-diisocyanate; hexylene-l6-diisocyanate; cyclohexylene-l 2-diisocyanate; M-phenylenediisocyanate; 3,3'-dimethyl-4,4-biphenylene diisocyanate; 3,3-dimethoxy-4,4'ciphenylene diisocyanate; 3,3 '-diphenyl-4,4'-biphenylenediisocyanate; 4,4-biphenylene diisocyanate;3,3'-dichloro-4,4'-biphenylene diisocyanate; triphenylmethanetriisocyanate; 1,5 naphthalene diisocyanate, or polyisocyanates in ablocked or inactive form such as the bisphenyl carbamates of tolunediisocyanate, etc.

Turning now to the reaction preventative liquid, there are a number ofcommercially available liquids known by the trade name, cellosolve, thatare manufactured and sold by Union Carbide for preventing the reactionof liquid organic resins and polyisocyanates. In the manufacture of thepolyurethane foam the particular cellosolve which has been found to bemost effective is ethylene glycol monoethyl ether. Other of thecellosolves can be used but are not as effective. Of course, the generalcharacteristics of the material must be such that it inhibits orprevents the reaction between the fluids being mixed and is compatiblewith the materials in which the gun-is manufactured. It is recog nizedthat if the gun is manufactured from polyvinyl chloride that the acetateversion of the cellosolve will react therewith and is thus undesirable.

In the experimental models, the cellosolve is injected into the chamberbefore the gun is completely assembled. This is done as follows: beforethe retaining ring and sealing plate 66 are fixed in position but afterthe piston and valving rod have been inserted into the barrel 12 suchthat the forward end of the rod 46 is somewhere in the slot'52, ahypodermic needle (connected to a supply of cellosolve) is passed downthe bore 44 of the forward section 40 and into the slot 52. At thispoint the cellosolve is pumped into the annular chamber via the slot'52until the chamber is filled. Then the assembly of the gun is finished bypushing the rod 46 into the bore 44 in the forward section 40. It will,of course, be appreciated that in the commercial embodiment, a valve oroperable port can be provided in the wall of the cylindrical section 23so as to permit the chamber for the cellosolve to be filled after assembly.

It will be appreciated that numerous changes and modifications can bemade to the embodiment described herein without departing from thespirit and scope of the invention.

- What'I claim is:

1. An apparatus for mixing and dispensing a plurality of liquids whichcomprises:

a. housing means;

b. a mixing chamber in said housing means having i. an outlet at itsforward end, and

ii. a plurality of entrance ports upstream of said outlet, each forintroducing fluid into said chamber;

0. a valving rod for opening and closing said entrance ports received byand slideably engaging said mixing chamber and reciprocally movabletherein, the forward end of said rod being movable to an open positionrearward of said entrance ports and movable to a closed position forwardof said entrance P means for moving said valving rod;

. means rearward of said mixing chamber into which said valving rod isretractable, said means defining a reservoir adapted to hold materialfor cleaning said valving rod; and

f. means for introducing cleaning material into said reservoir.

2. The apparatus as claimed in claim 1 wherein said means for movingsaid valving rod includes means defining a cylinder and a pistonreciprocal within said cylinder and wherein the rearward end of thevalving rod is mounted to said piston for movement therewith.

3. The apparatus as claimed in claim 2 wherein pneumatic means areprovided for moving said piston.

4. The apparatus as recited in claim 3 wherein said pneumatic meansinclude:

a. a source of compressed air, and

b. a handle and trigger assembly associated with said cylinder and saidsource of compressed air so that upon actuation of the trigger, thepiston is caused to move rearwardly and upon release of the trigger thepiston is caused to move forwardly.

5. The apparatus as recited in claim 1 wherein the reservoir includes aslotted member for guiding said valving rod in its reciprocatingmovement within said reservoir.

6. The apparatus as recited in claim 5 wherein at all times at least aportion of said rod is disposed within said slotted member.

7. The apparatus as defined in claim 1, wherein in the closed positionthe forward end of the valving rod is flush with the outlet end of saidmixing chamber.

8. The apparatus as recited in claim 1 wherein a cleaning material isdisposed within said reservoir and a portion of the valving rod withinthe reservoir is contacted by said material.

5 bination therewith:

9. The apparatus as recited in claim 8 wherein said reactionpreventative material monoethyl ether.

is ethyleneglycol 10. The apparatus as recited in claim 1 and in coma. apressurized source of liquid organic resin in communication with atleast one entrance port;

b. a pressurized source of liquid isocyanate in communication with atleast one other entranceport;

and

2. The apparatus as claimed in claim 1 wherein said means for movingsaid valving rod includes means defining a cylinder and a pistonreciprocal within said cylinder and wherein the rearward end of thevalving rod is mounted to said piston for movement therewith.
 3. Theapparatus as claimed in claim 2 wherein pneumatic means are provided formoving said piston.
 4. The apparatus as recited in claim 3 wherein saidpneumatic means include: a. a source of compressed air, and b. a handleand trigger assembly associated with said cylinder and said source ofcompressed aIr so that upon actuation of the trigger, the piston iscaused to move rearwardly and upon release of the trigger the piston iscaused to move forwardly.
 5. The apparatus as recited in claim 1 whereinthe reservoir includes a slotted member for guiding said valving rod inits reciprocating movement within said reservoir.
 6. The apparatus asrecited in claim 5 wherein at all times at least a portion of said rodis disposed within said slotted member.
 7. The apparatus as defined inclaim 1, wherein in the closed position the forward end of the valvingrod is flush with the outlet end of said mixing chamber.
 8. Theapparatus as recited in claim 1 wherein a cleaning material is disposedwithin said reservoir and a portion of the valving rod within thereservoir is contacted by said material.
 9. The apparatus as recited inclaim 8 wherein said reaction preventative material is ethylene glycolmonoethyl ether.
 10. The apparatus as recited in claim 1 and incombination therewith: a. a pressurized source of liquid organic resinin communication with at least one entrance port; b. a pressurizedsource of liquid isocyanate in communication with at least one otherentrance port; and c. pneumatic means for reciprocating said valving rodwhich means include a source of compressed air.